Various branches of industry more and more frequently use mass-produced parts, all in one piece, formed of alloys or other special materials having undergone heat treatments. Now, the latter may be very varied and, moreover they must satisfy very specific conditions. Hence there exists a need for installations permitting heat treatments to be effected, and comprising several elements, such as furnaces or hardening vats, arranged as a battery, and easily accessible.
Arrangements of elements permitting heat treatments to be carried out in precise and careful conditions, especially avoiding contact of the parts with the air as much as possible, are already known.
Thus, in Austrian Pat. No. 167,109, an installation is seen in which a removable-cover furnace can be displaced on a transport track above pits capable of containing various hardening vats and a charging box. U.S. Pat. No. 1,876,960 describes an annealing installation in which there is provided, below the furnace, a turntable capable of containing the charges. U.S. Pat. No. 3,381,947 likewise describes an installation with furnaces and hardening vats, as well as means for introducing the charges into the installation.
In all these known installations, there is found an arrangement comprising only a small number of elements, and which is of excessive bulkiness. Moreover, none of these installations perfectly protects the parts against the risk of oxidation.
Certificate of addition No. 95877 to French Pat. No. 1,555,588 discloses an installation in which a first set of elements is disposed in a row of furnaces opening horizontally on a transfer chute provided with a track on which elements of a second set, comprising one or more charging cars capable of being provided with hardening vats, can move. Such an installation is very bulky and involves continuous maintenance of the transfer chute under a protective atmosphere.
Installations which permit charges to be transferred from an open bottom removable-cover furnace directly into a hardening vat which has previously brought immediately beneath the furnace are described in German patent DE-1942801 and in the publication EP-A-0023546. However, these installations cannot be arranged so as to combine efficiently the use of several furnaces and several hardening vats or other auxiliary elements.